Black bears hold clues to muscle waste

HIBERNATING bears could show how to treat muscle wasting in humans who are confined to bed for weeks or months, or even help astronauts cope with space travel, scientists report today.

Studies of astronauts in weightless conditions and of bedridden patients show that muscles atrophy if they are not used. Yet the black bear, Ursus americanus, can keep its strength up over the three to five months it spends dozing in its den during the bitter North American winter.

Dr Hank Harlow, of the University of Wyoming, Laramie, said: "The black bear is doing something unique that has not been identified in our present treatment of human patients under prolonged bed rest. Understanding how they maintain their muscles during their starvation and confinement can potentially lead to new ways of looking at muscle disuse atrophy in humans."

His team reports today in the journal Nature that bears at the end of the winter had the same number and size of skeletal muscle cells as at the beginning, even though they had starved during hibernation. Dr Harlow and colleagues suggest that bears might keep their strength up by recycling urea in the gut to provide the building blocks for new muscle protein.